The present invention relates to a dental X-ray image acquisition system, to an X-ray generator, and to a command module for controlling an intra-oral sensor suitable for use in such a system.
In known manner, a dental X-ray image acquisition system mainly comprises an X-ray generator and an intra-oral sensor that is sensitive to said X-rays, and that is associated with a command module for acquiring the X-ray image.
The X-ray generator is required to be fitted with control means, generally a button, enabling the operator to trigger the emission of X-rays in manual and deliberate manner.
Such an X-ray generator is also fitted with a timer enabling the operator to set a predetermined duration for X-ray emission, it being understood that the operator can also voluntarily stop the emission of X-rays by using the above-mentioned control means.
In a first known system, the starting and the end of acquisition by the sensor are under the control of the generator.
In another known system, in particular as described in U.S. Pat. No. 5,331,166, X-ray sensitive pellets are integrated in the intra-oral sensor, said pellets being adapted to send a signal to the command module of the sensor which controls the starting and the stopping of digital image acquisition as a function of the intensity of said signal.
Also known, in particular from the disclosure of U.S. Pat. No. 5,694,448, is an imaging system in which the output level from a charge-coupled device (CCD) sensor is continuously monitored so as to detect when the generator is emitting X-rays, i.e. whenever said level becomes greater than a noise level. When such emission is detected, image acquisition proper is performed.
Given that the CCD sensor is read and emptied continuously in cyclical manner, in order to make a comparison with the noise level, a most unfavorable circumstance can arise during which no image is acquired even though X-rays have begun to be emitted by the generator.
In practice, 10% to 20% of the X-rays emitted by the generator can be lost in this way, and that is naturally harmful to the patient.
To sum up, none of the above-mentioned prior art systems is capable of optimizing the quantity of X-rays received by the patient since the practitioner can adjust the timer in intuitive manner only. In practice, practitioners prefer to use an overdose of X-rays in order to be sure of obtaining an image of good quality.